This invention is related to a mechanism for positioning a means for performing at least one operation at a selected one of at least two selectable spaced-apart operating positions and more particularly to such mechanism that is provided with at least one pair of oppositely acting resilient biasing means that are able to be sufficiently compressed by any resistance encountered during the positioning to apply a biasing force sufficient to place the mechanism in a preloaded condition sufficient to enable the operating means to perform the operation desired at the particular operating position when the resistance is overcome or otherwise is removed upon the occurance of an event enabling the operation to occur.